1. Field
The present invention relates to a hydraulic power transmission.
2. Description of the Related Art
Conventionally, a hydraulic power transmission such as a torque converter has been used as a starting device of a transmission of a vehicle. The torque converter includes a pump impeller, a turbine impeller coupled to the pump impeller via a hydraulic oil circulation circuit, and a cover member connected to the pump impeller to cover an outside surface of the turbine impeller. Many torque converters include a lock-up clutch capable of mechanically coupling the cover member and the turbine impeller to each other in order to enhance efficiency of the torque transmission.
In a torque converter including a lock-up clutch, vibration of a drive system occurs due to rotational fluctuation of the engine as the lock-up clutch is connected. Then, in order to reduce vibration of the drive system, it is common to interpose a damper mechanism such as a coil spring between a pump impeller and a turbine impeller. Further, in recent years, there is provided a torque converter including an auxiliary mass body and a spring, in which a dynamic vibration absorber (or a dynamic damper) configured to absorb or control excessive vibration is disposed to further reduce vibration. For example, Japanese Unexamined Patent Application Publication No. 2011-058557 discloses a torque converter in which a dynamic vibration absorber is directly attached to a turbine impeller. Also, Japanese Patent No. 4987617 discloses a torque converter in which a dynamic vibration absorber is disposed in an intermediate member disposed between a pump impeller and a turbine impeller, in an example illustrated in FIG. 4.